The present invention relates to a technique for assuring qualities, such as transfer rate and response time, in the operation of a storage system.
In recent years, broadband communications services have enjoyed widespread use. With this trend, media-rich contents, such as digitized movies and news, have been delivered by streaming technology more increasingly. Storage equipment, a storage system, or a storage array system contained in a system for delivery of streaming media is required to assure the qualities of data transfer (hereinafter referred to as qualities of services (QoS)), such as transfer rate and response time, as well as the maximum throughput performance, in order to assure stable delivery of data to clients. Prior techniques regarding such quality assurance are disclosed in Patent References 1 to 3.
Patent Reference 1 discloses a technique that is intended to assure communications qualities from a computer to storage areas of storage equipment while taking into account the components inside the storage equipment and their respective performance values. In particular, a communications quality-setting device for assuring communications qualities between the storage equipment and a computer is disclosed in Patent Reference 1. This quality-setting device has an assured performance value-creating portion and an assured performance value-setting portion. The assured performance value-creating portion determines a performance value to be assured in each storage area, based on information about requests regarding assurance of the communications qualities, on the assurable performance value of the interface of the storage equipment, and on the assurable performance values of the storage areas of the storage equipment. The assured performance value-setting portion assures communications between the computer and the storage areas inside the storage equipment by giving an instruction to a storage controller to control the arrangement of data between the storage areas and the interface according to the performance values to be assured.
Patent Reference 2 discloses storage equipment for assuring the data transfer rate. Specifically, Patent Reference 2 discloses a technique using an expected data transfer rate and the transfer rate of each track is disclosed. The storage equipment is informed of a required, expected data transfer rate. This rate is registered in a management table. During formatting, the storage equipment recognizes bad sectors, if any, by writing and reading of data to and from each track. The writing time to the sectors, excluding the bad sectors, is registered in the management table. If this data transfer rate is less than the already registered, expected data transfer rate, it is recognized that no data can be stored in this storage equipment. Data is stored using only the sectors which can assure the expected transfer rate.
Patent Reference 3 discloses storage equipment having a timeout table and a data creation means. A time at which access to data recorded in the recording portion should be terminated is recorded in the timeout table. If the access does not end when the time stored in the timeout table has passed, the data creation means gains access to redundant data recorded in the recording portion and creates data.
[Patent Reference 1] JP-A-2004-86512
[Patent Reference 2] JP-A-10-162505
[Patent Reference 3] Japanese Patent No. 3,080,584
In the aforementioned streaming the delivery system, the computer offering services to customers makes plural accesses simultaneously (hereinafter referred to as multiple streaming accesses) to a storage device in which the media-contents are stored, in order to deliver the contents to plural customers simultaneously. The “streaming” indicates transfer of a unit of data. For example, one stream corresponds to data transfer of one content. It is necessary that storage equipment treating multiple streaming accesses assure a predetermined quality of service (QoS) for each stream.
In the Publications described above, the assurance of quality of service regarding one stream is mentioned. However, with respect to multiple streams, how quality of service of each individual stream is assured is not mentioned at all.